ABSTRACT Alcohol (ALC) use disorder (AUD) is an unrelenting public health concern. Several medications have been approved for treating AUD, but these pharmacotherapies are not widely used, nor are they universally effective or appropriate to use in all AUD patients due to contraindications. To address the continued need to improve AUD treatment, identifying novel AUD pharmacotherapies is a high NIAAA priority. Preclinical studies show that chronic or binge-like ALC administration decreases extracellular glutamate levels, which are then increased during ALC withdrawal. These elevated glutamate levels observed during ALC withdrawal can be reduced with further ALC administration, driving a cycle of heavy ALC use and withdrawal periods that characterize AUD. The changes in glutamate homeostasis that occur during the cycle of chronic ALC intoxication and withdrawal have been attributed to altered glutamate transport (e.g., changes in cystine- glutamate exchanger [xCT] and glial glutamate transporter [GLT-1] expression and function). Normalization of extracellular glutamate levels (i.e., restoration of glutamate homeostasis) through administration of compounds like n-acetylcysteine (NAC), which increase expression of the xCT and GLT-1 following drug exposure, attenuates maladaptive brain changes produced by ALC, as well as ALC self-administration and behavioral sensitization in preclinical models. Preclinical data provide a strong scientific premise for the hypothesis that restoration of glutamate homeostasis is a promising pharmacotherapeutic approach for AUD, yet this research area remains unexamined in prospective clinical studies. The overarching goal of this application is to demonstrate that restoration of glutamate homeostasis with NAC is a viable strategy for treating AUD. This goal will be achieved through the conduct of a rigorous within-subject, placebo-controlled study that has been modeled from previous successfully reverse-engineered human laboratory approaches. This research will demonstrate the initial efficacy, safety and tolerability of NAC for treating AUD. This work will directly translate findings from preclinical research and provide basic science information about the glutamatergic mechanisms underlying the pharmacodynamic effects of ALC in humans. The proposed research will also expand the scope of current AUD treatment research by focusing on glutamate homeostasis, which has strong preclinical evidence supporting its critical role in AUD but remains unstudied in clinical research.